An exogenous substance provided to an individual may affect the functions of components of innate immunity, including natural killer (NK) cells and T lymphocytes. NK cells are a vital part of the innate immune system and play an important role against microbial infections and tumor surveillance through secretion of an array of cytokines including IFN-γ (Interferon-γ) and TNF-α (Tumor Necrosis Factor-α) and by cytolysis of infected or neoplastic cells. Toll-Like Receptors (TLRs) are involved in innate immunity by recognizing molecules that are broadly shared by pathogens, and they activate a cascade of signaling pathways, triggering NF-κB and type-1 interferon production. T cells are involved in the initiation and regulation of innate and adaptive immune responses. T cell subsets play specific roles in eliciting an immune response. Exposure to or administration of an exogenous substance may decrease CD4/CD8 cell ratios and alter T cell function including cytokine secretion and proliferation.
Substances such as cigarette smoke extracts may inhibit the secretion of cytokines such as IL-1β (Interluekin-1β), IL-2 (Interluekin-2), IFN-γ and TNF-α by Peripheral Blood Mononuclear Cells (PBMCs). Such proinflammatory cytokines are capable of driving NK cell and cytotoxic T cell responses that are critical to tumor suppression. Given the importance of these cell types in the immune response, it has been suggested that T cell and NK cell response resulting from smoking could significantly impair the ability to fight viral and bacterial infections as well as tumor surveillance.
While cigarette smoking has represented a most common form of tobacco consumption, non-combustible tobacco such as, moist snuff, snus, and other smoke-free products, also exist in the marketplace. Relative to cigarettes, health risks associated with the use of smokeless tobacco products have typically been shown to be lower.
The effect of cigarette smoking on immune function has been the subject of considerable research, but less is known of how the use of non-combustible forms of tobacco, including smokeless tobacco, electronic cigarettes or nicotine, may alter the immune response. For example, some in vitro studies suggest smokeless tobacco elicits immunostimulatory responses as observed by altered cytokine secretion. There has accordingly been a long-felt need for a process for assessing risk that a substance, such as a component substance of a tobacco product, will suppress immune competence in a population of subjects.
Cigarette smoke consists of a particulate phase and a gas-vapor phase. The particulate phase, dissolved in dimethyl sulphoxide (DMSO) (or alternate solvent) is known as Total Particulate Matter (TPM) and is commonly used in cell culture studies. A different method of exposing cells to cigarette smoke involves the use of smoke-conditioned medium generated by passing cigarette smoke through it; this preparation is referred to as cigarette smoke extract, whole smoke conditioned medium (WS-CM) or other types of aqueous extracts. Each of these Tobacco Product Preparations (TPPs) is chemically distinct and therefore could elicit different responses. Alternatively, whole smoke may be exposed to cells directly. Smokeless tobacco (ST) extracts may be generated in several different ways: for example, direct extraction in cell culture medium or extraction in complete artificial saliva (CAS) or other solvents.
It has been an open question how combustible and non-combustible TPPs modulate select immune responses in a population of subjects. There has accordingly been a long-felt need for a process for assessing risk that a substance, such as a combustible or non-combustible TPP, will suppress immune competence in a population of subjects.